Goal: To develop a multicultural quality of life (QoL) instrument specific to overweight youth for use in evaluating weight-management treatments and investigating environmental and psychosocial associations. Aims: 1) To develop a weight-specific QoL instrument in US English and Mexican-American Spanish using in-depth interviews and focus groups with African-American, Caucasian, and Mexican-American youth ages 11-18 in Western Washington and Southern California; 2) To validate cross-sectional psychometric and practical measurement properties of the new weight-specific instrument using classical psychometric and IRT analyses; 3) To explore associations of BMI with QoL and known or hypothesized correlates, 4) To assess the ability of the items and measures to detect change in a small cohort of youth participating and not participating in a formal weight loss program, and 5) To produce/disseminate final version of the instrument. Significance: The two-fold increase in overweight status among Caucasian youth in recent years is only overshadowed by the three-fold increases among minority youth, primarily Mexican-Americans and African- Americans. This disproportionate increase in overweight among minority youth may exacerbate pre-existing health outcome disparities and require innovative approaches to understanding their perspectives and to design and evaluate effective treatments that will reduce health disparities. Innovation: A QoL measure should be developed with full participation of the major affected cultural groups targeted for weight treatment. Simultaneous cultural development of measures in different ethnic groups with multicultural investigators in this study will meet this requirement. Methods and Analysis: A comprehensive conceptual model grounded in qualitative methodology will drive measurement development. In-depth interviews and focus groups with 120 overweight and at-risk youth will apply a needs-based model and culturally sensitive approach to instrument development. Generation of items in English and Spanish and cognitive debriefing, readability, and translatability analyses will be conducted. A validation sample of 360 youth (200 BMI 2> 95%, 80 BMI 85-94%; 80 BMI z 84%) will be recruited who will complete the new weight-specific instrument and other questionnaires. Factor analysis and item-response methods will be used for scale development. Evaluation of reliability, construct validity, effect sizes in a small cohort, and association with BMI will be examined. Power is estimated to be between 77-99% to detect differences with an effect size of .41 or greater using univariate and multivariate modeling to investigate known and hypothesized correlates. Investigators: Multicultural team of experienced outcomes experts, obesity experts, endocrinologists, and community agents will collaborate to recruit, study, publish, and disseminate results.